The reason is actually very simple. Sasuke Uchiha's personality is more elegant, giving people a very close feeling. Personally, I think Sasuke Uchiha is very attractive, especially the bright spots in some of his characters, which deserve our affirmation. In fact, attractive people are not necessarily the mainstream personality, a little maverick, and it is easier to attract everyone's attention. This is my personal opinion and the reason why I like Sasuke Uchiha.
As for Uchiha Itachi, he is actually very good. Many people like his handsome appearance, but his performance is a bit boring, so some people don't think much of Uchiha Itachi. Moreover, Uchiha Itachi's image is reflected in many cartoons, so he looks a little tired of aesthetics, which is one of the reasons why Uchiha Itachi is not liked by me. Handsome men can make people feel more attractive like Sasuke Uchiha.
Generally speaking, Sasuke Uchiha and Uchiha Itachi have similar scenes, and their contradictions are also of concern to everyone, but generally speaking, Sasuke Uchiha plays a more important role in Naruto, and Sasuke Uchiha has more skills, which is one of the reasons why he is handsome!